fuel injection systems diesel

Transcription

1/18/2010
Sistemas Automóveis
FUEL INJECTION SYSTEMS
DIESEL
Rui Manuel Vieira Pinto
1090039
Ano lectivo 2009/2010
1 - Basic diesel fuel systems
2 – Injection pumps
3 - Injectors
Fuel injection systems - diesel
4 - Inline injection pump
5 – Radial rotary injection pump
6 – Electronic injection systems
7 - Bibliography
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1 - Basic diesel fuel
systems
-Basic diesel engine operation
- Diesel engine force air by the intake valve
into the cylinder
- High compression ratio heats the air enough
to ignite the fuel)
Basic diesel fuel systems
- Fuel is injected into the cylinder at high
pressure
- The amount of fuel injected suits to the load
and controls engine speed
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- Basic diesel fuel systems
- Divided in 2 sections
- Low pressure side
- Clean the fuel
- Deliver fuel to high pressure side
Basic diesel fuel systems
-High pressure side
- Raise the fuel pressure high
enough to injection stage
- Basic diesel fuel system
- A lift pump takes fuel from the tank and keeps the
injection pump full with fuel (electric or mechanical, on
the engine or on the injection pump)
Basic diesel fuel system
- A filter removes water and large particles of the fuel
- A fuel filter removes extremely small particles
- Fuel under high pressure passes along injector pipes
(steel, with same length) to injectors by the action of
injector pump (synchronism with engine cycle)
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- Injector sprays fuel into combustion chamber
- Direct injection engine
- Combustion chamber not
divided
- Direct injection on
combustion chamber
- Superior efficiency
- Indirect injection engine
- combustion chamber divided
- Low noise level
- Low production costs
- More fuel consumption (10–15 %)
- Leak off pipes take excess of fuel back to the tank (also
remove air from the system)
- The combustion pressures are greater in a diesel engine than
in a similar gasoline engine (components stronger and heavier)
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- To make cold starting easier
- Extra fuel injection
- Combustion chamber heater
system (glow plugs) that can work
some minutes after the engine
start
2 - Injection pumps
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- High injection pressures needed to
- Exceed the compression
combustion chamber
pressure
in
the
- Exceed the combustion pressure in the
Injection pumps
combustion chamber
- Break up the fuel into small particles
INJECTION PUMPS
- Injection pumps
- Sent fuel to each injector
- under pressure
- In controlled quantities
- At the right time
Injection pumps
function of engine speed and load
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- Injection systems
- Types
- Inline pump injection
- Individual injection pumps
- Pump pipe injector (PLD)
- Unit injector (UI)
- Common rail
- Radial plungers injection pumps
- Axial plungers injection pumps
Injection pumps
- the next sections will analyze the inline pump and the radial rotary
injection pump
- PLD, UI and Common rail basic analysis is made in electronic
injection section
3 - Injectors
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- Sprays fuel into combustion chamber
- Mechanic type
- Electric types
- Electromagnetic – solenoid valve
Injectors
- Piezo electric
-
Mechanic type (typical)
- Fuel injection pressure exceed the injector spring
- The needle valve rises and fuel is sprayed in
combustion chamber
Injectors
- When injection ends, the pressure drop causes the
return of needle valve to the initial position
- Some of them can be tuned (spring strength adjust)
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- Electromechanic type
- Electronic control unit sends
electric signal to electro-valve
- A solenoid electric valve allows
fuel to pass to injector nozzle
Injectors
-Injection made in typical way
(already explained)
- In figure the injection pump
and the injector are a same unit
- Electric piezo Injectors
- Electromagnetic injector valve
replaced by electric piezo control
- Piezo effect - mechanical
distortion causes electric current
and vice-versa (Ex. quartz)
Injectors
- Injector control valve movement
with a 1 mm3 fuel precision
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4 - Inline injection
pump
-Traditional inline injection pump
- Have a pump element (plunger, cylinder) for
each engine cylinder
- Pump elements in line disposal
Inline injection pump
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-Traditional inline injection pump
- Body
- Crankcase
- Camshaft
- Feeding pump (or not)
- Pushers (or not)
- Visit window
-Gear rack
- Pump elements (plungers,
cylinder, gear)
- Feeding collector
- Retention valves
- Automatic speed regulator
- Camshaft
- It have the same rotation as the engine camshaft
(one turn for two turns of the crankshaft)
-Causes an linear movement on the plungers
-Plungers
- Push the fuel in the direction of the injector
- Gear rack
-Causes an rotation movement on the plungers
that is function of the accelerator pedal
- Pump elements
- Control the amount of fuel that goes to the
injector
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1/18/2010
- Basic operation
- The eccentric on the camshaft causes
constant linear movement of the pushers
- the plungers, by the action of the
pushers, push the fuel in the direction of
the retention valve
- the pressure is high enough to open the
retention valve and the fuel is conducted
by pipes to the injectors
- the amount of fuel is controlled by the
gear rack
- Basic operation
-The gear rack causes an rotation movement to the plunger that is
function of the accelerator pedal
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1/18/2010
- Basic operation
-The plunger has cannelures around it self to fuel flow, and the
position of the rack determines the position of the plunger that
determines the amount of fuel injected
- Basic operation
- The end of injection occurs when the cannelure of the plunger
reaches a position that makes connection between the cylinder and
the feeding collector, balancing the pressure
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1/18/2010
5 – Radial rotary
injection pump
- Radial rotary injection pump
- Used on small diesel engines
- Low volume and weight
Radial rotary injection pump
- High efficiency
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1/18/2010
- Radial rotary injection pump
- It will be studied the VR BOSCH radial
rotary injection pump
- One pump element for all the engine
cylinders
- Presence of internal sensors (fuel
temperature, rotation angle)
- Has a pump control unit, independent
from the engine control unit
- Components
- Low pressure side
- Fuel pump (actuated by VR
pump shaft)
- Pressure regulator valve (to
avoid high pressures caused by
pump high rotation in engine
high speed)
- Overflow valve (let fuel passes
to tank when a default pressure is
achieved, air automatic bleed off
made easily)
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1/18/2010
- Components
- High pressure side
- High pressure electro-valve
- Controlled by pump control unit
- Determines the injection flow
- Determines the injection duration
- Components
- High pressure side
- Fuel high pressure caused by radial plungers
- In figure: 3 possible
plungers disposal
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1/18/2010
- Basic
operation
-Distributor functions
- Send fuel to plungers
- Time duration in close position
of electro-valve determines the
injection flow
- Basic
operation
-Distributor functions
- Send fuel to injectors
- The plungers are pressed by
cam
-Fuel high pressure generated
- Distributor rotates to injector
flow position
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1/18/2010
- Basic
operation
-Advance elements
- Change the injection moment
- Analyses crankshaft position
and rotation angle sensor
-Rotate cam causing delay or
advance on injection
- Controlled by control unit
(hidraullic control with electrovalve)
6 – Electronic
injection systems
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1/18/2010
- EDC (Electronic Diesel Control)
- UI (Unit Injector)
Electronic injection of Diesel Engines
- PLD (Pumpe Leitung Duse)
- Common Rail
- Main objective
- Reduce air pollution caused by
diesel combustion
- Fuel quantity injection electronic
control
Electronic injection of Diesel Engines
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1/18/2010
- Used on VOLVO trucks
EDC (Electronic Diesel Control)
- Electronic control of the fuel injection
- Mechanical governor replaced by a fuel
electromagnetic control device controlled by the
electronic control unit
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- Electronic control unit
- Receives sensors information
- Calculate the amount of fuel to be injected in
function of engine load
- Generate failure codes (if necessary)
- Sends orders to the fuel control device
- EDC components (sensors and input signals)
- Test socket
- Accelerator pedal sensor (potentiometer)
- Contact of the brake pedal
- Contact of the clutch pedal
- Turbo load pressure sensor (electric signal in proportion of the
turbo pressure + atmospheric pressure)
- Air temperature sensor in admission (NTC resistance)
- coolant temperature sensor (NTC resistance)
- 2 x Rotations sensor
- Velocity sensor
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1/18/2010
- EDC components (actuators and output signals)
- Diagnosis lamp (blinks to give failure code – Ex. coolant
temperature, turbo charge, air temperature in
admission, tension on the alternator belt )
- Electromagnetic fuel control device
- Cut of injection (In emergency situations done by a
pneumatic valve that acutates in injection pump)
- EDC electronic control unit
- By default from factory:
- Speed limit
- Maximum constant rotations
- Programmed constant speed
(maximum and minimum)
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- EDC electronic control unit
- Special functions:
- Constant speed programmer (Keeps the
same speed independent of the load)
- Constant rotations programmer (Engine
keeps constant rotations independent of
the load – Ex. winch)
- Stop engine by start key instead of a
mechanical way
- Maximum rotations limited in cold
running
-Electromagnetic fuel control device (components)
- Composed by an electromagnet that controls the injection
pump rack (see in line pumps)
- Position sensor that inform the electronic control unit about
the pump rack and determines the intensity of the electric
current in the electromagnet
- Rotations sensor (2x) – One in the electromagnetic fuel
control device (principal) and another (reserve) given by the
tachometer
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- Used on VOLVO trucks, VW automobile diesel
engines, CATERPILLAR engines
UI (UNIT INJECTOR)
- Injector units controlled by the electronic control
unit
- Electronic control unit
- Calculates and controls the amount of fuel that
will be injected (duration of injection)
UI (UNIT INJECTOR)
- Calculates and controls the injection angle
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1/18/2010
- Electronic control unit - sensors and cut switchs
- Velocity sensor
- Crankshaft rotations sensor
- Accelerator pedal sensor
- Identification of cylinder sensor
- Clutch pedal switch
- Brake pedal switch
- Air temperature sensor in admission
- Coolant temperature sensor
UI (UNIT INJECTOR)
- Injection process
- Electric signal sent to the electric valve of the
injector unit closes it
UI (UNIT INJECTOR)
- Fuel return system closes and injection pump
movement causes high pressure
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1/18/2010
- Injection process (cont.)
- Injection of fuel in cylinder when injector opens
(about 400 bar)
UI (UNIT INJECTOR)
- During injection, pressure reaches 1600 bar
(caused by injector nozzles)
- Injection ends when the electric signal stops
opening the electric valve (spring) and return,
reducing the pressure
-Injection angle
- Definition: Rotation angle of crankshaft in
reference with Top Dead Center (injection point) –
18⁰ before or 6⁰ after the TDC
UI (UNIT INJECTOR)
- Crankshaft rotations sensor information is used to
determine when electric valve of fuel should open
or close
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1/18/2010
- Cylinder balance (to cause smooth and regular
low speed) – only occurs in low speed
- Electronic control unit determines, in each
injection, the speed and acceleration of the
engine wheel in order to determine if there is
the same power in each cylinder
UI (UNIT INJECTOR)
- If not the electronic control unit compensates
by the duration of injection
- Fuel amount limit
- Electronic control unit determines the amount
of fuel to inject with restrictions such as:
UI (UNIT INJECTOR)
- Speed limit
- Rotations limit
- Toxic gases limit
- High temperature limit
- Engine protection
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1 - In the rise of plunger (return
spring + plunger control) the electric
valve is open (input of fuel in the
cylinder)
2 - Plunger control pushes plunger
down, the fuel returns while the
electric valve is open
3 –an electric signal is sent to the
electric valve closing it, the pressure
of fuel rises until overcome de
injector resistance - injection
4 – Injection ends when electric valve
cuts off (opens) and pressure
decreases
UI (UNIT INJECTOR)
- Notes about injection
- Superior injection pressure (2000 bar) in
comparison with inlines and rotary pumps
UI (UNIT INJECTOR)
- Plunger always completes its course, however
the amount of fuel depends of the electric valve
controlled by the electronic control unit
- As seen before there are limits to the amount
of fuel injected
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1/18/2010
- Pumpe = pump, Leitung = pipe, Duse = injector
- Used on MERCEDES BENZ trucks
PLD (Pumpe Leitung Duse)
- to comply with new rules of gases emission
- Engine controlled by an electronic module
(microcomputer) programmed
- Electromechanical injection system
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1/18/2010
-Electronic module (PLD)
- Injection angle determined by an
encoder information (assembled on the
engine wheel) that measures the piston
speed
- Sensors information + PLD program
parameters + ADM (administration
module) determines the beginning and
duration of injection
- ADM (administration module)
- Data acquirer of maximum and minimum
values of
- Engine rotation
- vehicle speed
- torque
- Interaction with other modules (CAN) as
- Brake system (ABS)
-PLD
- Automatic transmission
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1/18/2010
- ADM (administration module)
- Control cabin equipment
- Control of accelerator pedal (If it fails, vehicle
change to low speed and ADM rotation
management takes control)
- Due to functions parametrization characteristic
there are several possible functioning modes to
vehicles
-If failure, the PLD impose a 1300 rpm constant
value
- Electromechanical fuel injection components
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1/18/2010
- Electromechanical fuel injection stage 1 - Admission
-The cam position makes
spring pull down the
plunger
- The electromagnetic valve
spring allows the cylinder
to be filled with fuel by
pump action
- Electromechanical fuel injection stage 2 - previous course
-The cam pushes up the
plunger
- The electromagnetic valve
remains open and the fuel
returns (plunger pressure is
higher than the pump’s
one)
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1/18/2010
- Electromechanical fuel injection stage 3 - injection
-The electromagnetic valve
closes (energized by control
unit)
- The plunger keeps it’s
upside movement
- The fuel is sprayed by the
injector in combustion
chamber (up to 1600 bar)
- Electromechanical fuel injection stage 4 – residual course
-The electromagnetic valve
opens (deenergized by the
control unit)
- The plunger keeps it’s
upside movement
- The fuel returns to the
tank
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1/18/2010
- The fuel is pressurized in a distribution pipe (rail)
COMMON RAIL
- The distribution pipe (rail) is common to all
cylinder
- Injection is made with electromagnetic valves (up
to 1400 bar)
- Components
- Tank
- Pipes
- Water separator filter
- Manual pump (to bleed off air),
- Water sensor - water may cause cavitation, a
frequent cause of structural damage
- Bleed off screw
COMMON RAIL
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1/18/2010
- Components
- Low pressure circuit
- Gear pump (5 to 13 bar) ensures fuel supply to main
filter and to high pressure
pump
- Filter
- Security pressure valve
- Fuel control electro-valve
(control the amount of fuel
by ECU to high pressure
pump)
COMMON RAIL
- Components
- Fuel control electromagnetic valve
- PWM (pulse wave
modulation) control
- Rail fuel quantity
controlled by opening time
(more rail pressure means
more open time
COMMON RAIL
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- Components
- High pressure circuit - rises the fuel pressure to
levels that allow pulverization
- Plungers (3 or more) pump
- Retention valve to avoid rail
fuel discharge
- Security valve (returns fuel
to tank)
- distribution pipe (rail)
- High pressure pipes
- Injectors
COMMON RAIL
- Components
- Plungers pump
- Fuel transfer to rail, pipes and
injectors
- Gear pump (by engine
mechanical distribution
- No engine synchronism needed
COMMON RAIL
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- Components
- Injectors
- Injection duration controlled by
ECU (sensors information)
- Fuel quantity depends of
electro-valve opening time, fuel
pressure and injector type
COMMON RAIL
6 - Bibliography
37
1/18/2010
2 - http://www.asme.org/ (American Society of mechanical engineers)
[Consult. Nov. 2009].
3 - http://rbkwin.bosch.com/za///en/powerconsumptionemissions/dieselsysteme/dieselsy
stem/passenger-car/injection_systems/index.html
1http://files.asme.org/asmeorg/Communities/History/Landmarks/10001.pdf
4http://www.google.pt/imgres?imgurl=http://moodle.student.cnwl.ac.uk/moo
dledata_shared/CDX%2520eTextbook/dswmedia/images/heuidieselinject.jpg
&imgrefurl=http://moodle.student.cnwl.ac.uk/moodledata_shared/CDX%2520
eTextbook/dswmedia/fuelSys/diesel/elec/heuidieselinject.html&h=280&w=35
0&sz=55&tbnid=N2Sl3kg7ZTStM:&tbnh=96&tbnw=120&prev=/images%3Fq%3D%2522diesel%2Binjection%
2Bsystem%2522&hl=ptPT&usg=__YQ8g0kdi7Y4w6E2DcLqkRrEImo0=&ei=pU4KS_CPHcy2jAfR0aj3AQ&
sa=X&oi=image_result&resnum=1&ct=image&ved=0CAkQ9QEwAA
5http://www.lydallfiltration.com/tech/documents/DesignandPerformanceDiese
lFuelFilters.pdf
[Consult. Dez. 2009].
38
1/18/2010
7http://www.dieselpowermag.com/tech/general/0809dp_stanadyne_db2_injec
tion_pump/photo_02.html
6http://images.google.pt/imgres?imgurl=http://www.tpub.com/content/engine
/14081/img/14081_29_8.jpg&imgrefurl=http://www.tpub.com/content/engin
e/14081/css/14081_29.htm&usg=__h5J7mpqaPFV24BuuHAThDdRaMI=&h=491&w=384&sz=23&hl=ptPT&start=1&um=1&itbs=1&tbnid=GxsUfyBUzD_iDM:&tbnh=130&tbnw=102&
prev=/images%3Fq%3Ddiesel%2Bfuel%2Bfilters%2Boperation%26hl%3DptPT%26sa%3DN%26um%3D1
8 - http://www.emeraldinsight.com/fig/0330220301001.png
10 – Da Silva, Edson – Injecão Electrônica de Motores Diesel, EDC, PLD, UI e
Common rail, conceitos básicos funcionamento e manutenção, Ensino
Profissional Editora, ISBN 85-99823-05-1
9 – BOSCH – Bombas rotativas de inyección de émbolos radiales, para motores
diesel VR, control electrónico del motor para motores diesel, Instrucciónj
Técnica Edición 1999
11 – De Imperial, Juan Miralles – Bombas de Inyeccion Diesel, Biblioteca del
automóvil, Ceac, ISBN 84-329-1110-0
12 – Costa, António Alves, Mecânica Automóvel para o Exame de Pesados,
Edições Alves Costa, ISBN 972-8073-05-4
39

fuel injection systems diesel

Transcription

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